This invention relates to a method of launching inflatable airship apparatus for subsequent ascent to high altitude for operation as an airship. The invention is particularly, but not exclusively, involved with the launching of unmanned airship apparatus. The invention also relates to airship apparatus and to an airship launch station.
High altitude airships are designed to carry large payloads to high altitude and then to remain in a geo-stationary orbit for extended lengths of time. While there are many challenges facing the design of such an airship one of the primary ones is that of effecting a controlled launch of the vehicle.
The operation close to the ground of a high altitude airship, which is an extremely lightly constructed vehicle, requires levels of thrust and control that cannot be provided by the vehicle itself in anything more than absolutely calm conditions. Due to the difficulty in predicting these calm conditions it is almost impossible to provide a guaranteed launch capability for operational efficiency. Further to this, challenges exist in the provision of a safe means of recovery following the completion of a mission. In particular it is difficult to maintain operation of the envelope pressure system which maintains the pressure within, and hence the shape of, the airship""s envelope. The envelope pressure system is only required to function during launch and recovery of the vehicle and thus is subject to cold soak for potentially several years prior to descent and recovery. If conventional internal ballonet xe2x80x9csacsxe2x80x9d are employed, this cold soak may render the internal ballonet xe2x80x9csacsxe2x80x9d inoperative by the freezing action of water vapour within the envelope effectively bonding the sacs to the envelope. This would result in the loss of the vehicle during the descent phase of the mission due to lack of envelope internal pressure and ensuing structural failure.
Significant experience has been gained in the launching (and recovery) of meteorological balloons over many years. These balloons are vertically launched in a low state of helium fill and as they ascend to altitude the helium expands and they take on their full xe2x80x9chot air balloonxe2x80x9d shape. However such balloons are un-powered and effectively drift with the prevailing wind. The balloons remain in the vertical position throughout their flight.
An aim of the present invention is to provide an improved method of launching high altitude airship apparatus.
According to one aspect of the present invention there is provided a method of launching inflatable airship apparatus for subsequent ascent to high altitude for operation as an airship having a hull formed from an inflated flexible gas containment envelope, payload means, drive means mounted at the stern of the hull and cable suspension means, for supporting the payload means within the hull, connected to said drive means and to the hull at, or adjacent to, a nose portion of the hull, the method comprising partially inflating said gas containment envelope with a lighter than air gaseous medium to cause said nose portion to fill with said gaseous medium and to rise within a vertical launch enclosure to position the partially inflated gas containment envelope in a launch position, and subsequently releasing the partially inflated gas containment envelope from its launch position through an open top of the vertical enclosure so that the envelope ascends clear of the vertical enclosure and lifts the payload means and drive means by means of the cable suspension means.
The method according to the invention allows for the controlled release of the airship apparatus from a vertical enclosure. The airship apparatus can be held in its launch position ready for launch until the prevailing weather conditions are satisfactory for launching. As the airship apparatus ascends, the gaseous medium, e.g. helium, within the gas containment envelope starts to expand and the envelope takes on a fuller form. As the shape of the airship starts to form, the centre of gravity of the vehicle starts to rotate around the centre of lift ultimately resulting in the airships hull rotating to a level flight capable attitude. The drive means can then begin to function and the vehicle can be propelled and flown in the manner of a standard airship.
Vertical launching of the airship apparatus is performed with a far higher certainty of success than conventional launching procedures. The design centres around a launch station, typically in the form of a cylindrical building with a removable roof. Such a launch station allows the airship to be filled with the gaseous medium, e.g. helium, and prepared for flight in a weather proof environment. With local weather forecasting, a small local weather window can be predicted with certainty. At the appointed moment the roof is retracted and the airship apparatus ascends vertically out of the top of the building. The ascent then follows a typical meteorological balloon pattern until xe2x80x9croll overxe2x80x9d is achieved whereupon and the now-formed airship is flown to its site of operation.
Preferably the top of the vertical launch enclosure is provided with an openable closure which is normally closed to protect the enclosure from the elements but which is opened when the partially inflated gas containment envelope is ready for release from its launch position.
Preferably the rise of the gas containment envelope to its launch position and subsequently through the open top of the vertical launch enclosure is restrained by cable retaining means. The cable retaining means suitably comprises a number of restraining cables connected to the gas containment envelope and winch means for paying out the restraining cables to control the rise of the gas containment envelope. The connection of the restraining cables to the gas containment envelope is suitably released after the lifted drive means has risen above the top of the vertical launch enclosure.
Suitably only a minor proportion, e.g. from 5-10%, preferably from 6-8% of the fully inflated volume of the gas containment envelope is initially filled with said gaseous medium, e.g. helium, at standard temperature and pressure (STP).
Conveniently, solar cell means for powering the airship in operation are secured to the gas containment envelope when the latter is in its launch position.
According to another aspect of the present invention there is provided inflatable airship apparatus intended for ascending to high altitude for operation as an airship having an elongate hull, the airship apparatus comprising a gas containment envelope inflatable to form said elongate hull, payload means inside said gas containment envelope, drive means joined to the envelope at a region of the latter destined to form the stern of the inflated hull and cable means connecting the payload means and the drive means to a connecting portion of the gas containment envelope destined to be at the bow end of the inflated hull, the cable means being arranged to support the weight of the cable means and drive means from the said connecting portion when the gas containment envelope is partially inflated and arranged with its bow end uppermost.
According to a still further aspect of the present invention their is provided a launch station for launching inflatable airship apparatus to high altitude, the launch station including a vertical enclosure, a launch pad at the bottom of the vertical enclosure for enabling airship apparatus at the bottom of the vertical enclosure to be partially inflated with lighter than air gaseous medium so that a nose portion of the airship apparatus is able to rise within the vertical enclosure to a launch position, openable and closable closure means at the top of the vertical enclosure, and restraining means for connection to airship apparatus to be launched for controlling ascent of the airship apparatus from the launch pad to the launch position and subsequently from the launch position through the top of the enclosure with the closure means in its open position.
Suitably a collar is inflated about an opening at the top of the vertical enclosure.